Objectives: Although the fertilization and cleavage rate of implanted embryos is about 70%-90% in most patients, only a small number of embryos grown in vitro have the potential to implant. This indicates that many factors are responsible for a successful implantation, including obtaining viable embryos for transfer. This study aimed to examine the clinical results of pregnancy and implantation rates between day 2 and day 3 embryo transfer (ET) in women under the age of 40 experiencing fresh intracytoplasmic sperm injection-embryo transfer (ICSI-ET) cycles.

Materials and Methods: In a retrospective study, a total of 284 ETs were examined from March 2013 to December 2014. The transfer was done according to physician’s preference, patient characteristics or number of embryos available.

Results: The data suggested that clinical (35.4% vs. 28.9%, P = 0.26) or ongoing pregnancy (32.5% vs. 23.7%, P = 0.11) or implantation rate (0.267 ± 0.2 vs. 0.216, P = 0.09) was slightly better and the miscarriage rate (3.1% vs. 7%, P = 0.153) was slightly lower on day 3 ET vs. day 2, however, this difference was not significant. Although most of the baseline characteristics were similar between groups, the number of high-quality embryos (5.29 ± 3.9 vs. 4.47 ± 3.05, P = 0.011) and average embryo cleavage score (2.85 ± 0.4 vs. 2.25 ± 0.3, P < 0.001) was significantly higher in the day 3 ET in comparison to the day 2 ET.

Conclusion: A similar clinical outcome between ET performed on days 2 and 3 in women younger than 40 years undergoing fresh ICSI-ET is suggested by the results of this study.